1. Field
The present invention relates generally to communication, and more specifically to techniques for transmitting overhead information in a wireless communication system.
2. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, multi-media broadcast, text messaging, and so on. These systems may be multiple-access systems capable of supporting communication for multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems. A CDMA system may implement Wideband CDMA (W-CDMA), cdma2000, and so on. W-CDMA is described in documents from a consortium named “3rd Generation Partnership Project” (3GPP). cdma2000 is described in documents from a consortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available.
W-CDMA and cdma2000 employ direct sequence CDMA (DS-CDMA), which spectrally spreads a narrowband signal over the entire system bandwidth with a spreading code. DS-CDMA has certain advantages such as ease of supporting multiple access, narrowband rejection, and so on. However, DS-CDMA is susceptible to frequency selective fading, which causes intersymbol interference (ISI). A complicated receiver with an equalizer may be needed to combat the intersymbol interference.
A wireless communication system may send various types of transmissions such as a user-specific or unicast transmission for a specific user, a multicast transmission for a group of users, and a broadcast transmission for all users within a broadcast coverage area. The multicast and broadcast transmissions may be variable in nature, e.g., sent at variable data rates that change over time. In this case, overhead/control information for the multicast and broadcast transmissions may be sent on a control channel to indicate when and how each transmission is sent. Depending on how the control channel is transmitted, a terminal may need to continuously decode the control channel in order to obtain control information for each transmission of interest. This continuous decoding of the control channel can deplete battery power and is undesirable.
There is therefore a need in the art for techniques to send overhead information such that a terminal can efficiently receive transmissions of interest with reduced power consumption.